1. Field of the Invention
The present invention relates to a transmission for selectively driving a working machine, like a mower, which is attached to the belly or the rear portion of a working vehicle, enabling a working machine attached to the belly portion thereof to be prevented from inertial idling.
2. Related Art
Japanese Utility Model Publication No. 7-15784, for example, discloses a conventional transmission for driving a working machine attached to the belly or the rear portion of a working vehicle. The transmission comprises a transmission casing and an output casino, attached to the bottom of the transmission casing, which supports a mid-PTO shaft. A rear-PTO drive train is located at the rear portion of a running speed changing unit in the transmission casing. The mid-PTO shaft is driven below the rear-PTO drive train. A rear-PTO clutch mechanism is separated from a mid-PTO clutch mechanism.
When the output casing supporting the-mid PTO shaft is separated from the transmission casing as described above, the joint surfaces of the transmission casing and the output casing must be ground to be smooth and a seal must be placed between them when joined. This results in an increase in: the number of necessary parts, the steps in the assembly process and the manufacturing cost. Additionally, the PTO transmission unit is disposed separately from the running transmission unit at the rear of the transmission casing, while a part of the rear-PTO drive train constituting the PTO transmission unit is used for a part of a mid-PTO drive train. Thus, the mid-PTO shaft is disposed near the rear of the transmission casing so as to enlarge the transmission mechanism for transmitting power to the working machine attached to the belly portion of the working vehicle. Also, since the output casing projects downwardly from the lower surface of the transmission casing, the ground clearance of the working vehicle is reduced. Further, since each of the rear-PTO and mid-PTO clutch mechanisms are separate, they each require a separate PTO clutch lever which is confusing for the operator.
Japanese Utility Model Publication No. 7-15784 also discloses a brake unit disposed in a drive train for a working machine to prevent a working machine attached to the belly of a working vehicle from inertial idling. The brake unit for prevention of inertial idling is disposed around the mid-PTO shaft in the output casing so as to be in line with the mid-PTO clutch mechanism disposed therearound. The brake unit for prevention of inertial idling is constructed so as to act when a mid-PTO clutch lever is turned off or a clutch pedal is trod.
However, the brake unit for prevention of inertial idling acts only when the mid-PTO clutch lever disengages the mid-PTO shaft or the clutch pedal is trod. Then, if the object to be driven is shifted from the mid-PTO shaft to the rear-PTO shaft, for example, as soon as the clutch pedal is depressed the idled mid-PTO shaft, which has been stopped, begins to rotate again by the inertial force of the working machine. Additionally, a link mechanism interlocking the brake for prevention of inertial idling and the clutch mechanism, which is located outside the transmission casing, must be positioned to avoid other link mechanisms and is liable to rust due to its exposure to dust or water, thereby causing inferior movement.